Universal Serial Bus (USB) technology is widely used for communicating data between a computer system and a peripheral device. The USB technology provides interface standardization for connecting peripheral devices, such as a mouse, a printer, a modem, or a speaker with computers. The USB is a type of a serial port supported by a consortium of personal computer manufactures, such as Intel, Compaq, Microsoft, Philips, IBM, and NEC.
The full speeds of a serial port and a USB port are 100 Kbps and 12 Mbps, respectively, for data transmission. Accordingly, various devices may be connected through the USB port without speed limitation. When a computer is in use and peripheral devices are connected through the USB port, the connections are automatically recognized. The peripheral devices connected through the USB port do not need to have internal power supplies. The reason is that power is supplied from a USB host. For example, peripheral devices can connect to a USB host such as a computer through the same USB port without additional software or hardware. Therefore, the number of ports can be drastically reduced. Accordingly, the size of electronic devices, such as a portable terminal, can be minimized.
According to a USB standard, the two terminals connected through a USB port are a host and a USB device, respectively. The host controls the topology management of a bus, the monitoring of a USB device state, device control, and data transmission management through a bus, and supplies a predetermined operating voltage (i.e., a power supply voltage VDD) to the USB device.
As described above, most computers include a USB port such that it is unnecessary to install complex and various adaptors. When data is transferred from a mobile phone or a digital camera to a computer, the USB port is widely used. Due to this convenience of a USB port, terminals connected according to a USB standard (i.e., a USB interface standard) become more extensively used in different applications. That is, the USB standard is utilized to support an external communication between individual terminals, such as a mobile phone or a personal computer, and also to support internal communication (i.e., a local communication) between chips integrated in one system. Accordingly, different USB standards are set depending on application (i.e., according to an external communication between individual devices and an internal communication between chips). In this case, a new USB device is in demand, which performs communication according to different USB standards through one port. Thus, it is necessary to develop a new USB device capable of performing communication in different USB interface standards according to various hosts.